Includes: 3 pole, 4 position rotary switch, ¼" output jack and black chicken head knob. Hammond 1600 series transformers all provide secondary impedances of 4, 8, or 16 ohms but due to the unique wiring of the secondary, the impedance cannot be changed without rewiring... Until now. We now offer a selector switch, pre-wired and complete with ¼" output jack. Follow simple instructions provided to wire transformer secondary to switch, mount switch and ¼" jack in separate 3/8" diameter holes in chassis and you'll easily be able to select output impedance as necessary.